Recently, a vehicle-mounted driving recorder has been developed that can automatically record an image of outside or inside of a motor vehicle (an automobile) during driving and that can make an after-the-fact analysis on an objective situation at a time of an accident or a hiyari-hatto, in other words, at a time when a driver feels chill because he or she is close to be involved in an accident, and there is a trend that this kind of driving recorder is mounted on, for example, a taxicab in order to prevent an accident by making the after-the-fact analysis on an ordinary driving or to collect an objective evidence of a cause of the accident when the accident occurs.
Concretely, the driving recorder of this type is mounted on a vehicle, and so arranged to sequentially and chronologically store situation data such as outside image data, acceleration data, speed data and position data while the vehicle is driving in a memory so that an after-the-fact analysis can be made by reference to the situation data stored in the memory.
In order to record this situation data (store this situation data in a memory), conventionally known are an arrangement wherein all of the situation data during driving is stored until the capacity of the memory runs out, an arrangement of, so-called a ring-buffer memory method wherein the oldest situation data is updated in sequence when the capacity of the memory runs out, and an arrangement wherein, a hiyari-hatto, an accident or an abnormality is considered to occur at a time when an acceleration (a deceleration) of the vehicle shows above a certain numerical value, the situation data alone during a certain period before and after the time of the event is recorded in a nonvolatile memory to use the situation data for after-the-fact analysis from a transient memory (refer to the patent document 1).
With the above-mentioned conventional driving recorder, however, since the situation data during an ordinary driving is also recorded as well as the situation data at a time of an accident and at a time of a hiyari-hatto, it becomes difficult to make an after-the-fact analysis. More specifically, since the former two conventional driving recorders record all of the situation data, it becomes extremely difficult to extract the situation data at a time of a hiyari-hatto that is difficult to specify the timing unlike an accident.
In addition, with the later conventional driving recorder, since a lot of unnecessary situation data is obtained because the acceleration sensor reacts to a movement of just opening or closing the door or a quick acceleration or deceleration due to a driver's preference although a certain level of filtering is provided by the acceleration, it becomes very troublesome to select unnecessary situation data after the event.
A driving recorder that selects and stores only the situation data whose importance is high in a recording media generally uses acceleration data as a trigger for detection and the situation data before and after a time when the acceleration is detected in case the acceleration is bigger than a certain level is stored in the recording media (Patent document 1).
If the acceleration data is used as the trigger for detection, however, there is a problem of failing to record the situation data relating to a minor accident wherein the acceleration is small.
Patent document 1: Japan patent laid open number 5-197858